1. Field of the Invention
Embodiments disclosed herein relate generally to methods of inhibiting the deposition and/or crystallization of salt. More specifically, embodiments disclosed herein related to inhibiting the deposition or crystallization of particular sodium chloride salts from brine solutions. Other embodiments disclosed herein relate to methods of enhancing the adsorption and retention of the salt inhibitors, in particular salt inhibitors containing urea and urea analogues, for prolonging the lifetime following a salt inhibitor squeeze treatment.
2. Background Art
Aqueous streams comprising salt are produced and/or treated in a number of industrial processes. Such aqueous streams are often referred to as brine, which are solutions essentially saturated with various salts. Brines commonly include sodium chloride and chlorides of potassium, calcium, and magnesium, along with smaller quantities of salts comprising barium, strontium, iron and lead, all of which are collectively referred to herein merely as salt.
Oil reservoirs often contain high salinity brines in the form of connate waters contained within porous rock formations. These brines are produced along with hydrocarbon liquids and gasses. Such brines may cause production problems when they precipitate solid salt materials that can block pores and accumulate in and on pipes and other production equipment. The relative amounts of the salts vary with the mineralogy of the formation rocks that the connate waters have contacted. These brines may also be saturated and/or supersaturated at temperatures above surface temperatures. As brines are brought to the surface, the cooling of these brines and/or the evaporation of water from these brines as a result of oilfield production operations can cause the dissolved salts to crystallize from solution and deposit as solids. The precipitation of salts from these aqueous streams significantly reduces production of hydrocarbons to the point where remedial action is required, usually involving the re-dissolution of salt using fresh water or low salinity brine. Remedial actions thus require production operations to be limited or even to stop, and often need to be conducted at regular intervals, usually at relatively short regular intervals on the order of days or even hours depending on the location of the well and/or other variables.
In typical oil field applications, the concentrated brines in underground strata are usually saturated solutions at elevated temperatures, i.e. in the neighborhood of 90 to 300 degrees Fahrenheit. The temperature of the brine is reduced as it moves toward the earth's surface in the petroleum recovery process. As the temperature falls, the dissolved salts of the brine tend to come out of solution, usually in the form of crystals on the inner surface of the well bore and associated piping, pumps, rods, and the like. It is not unusual in certain geographic areas for salt deposits to interfere with pump operations or to completely block the flow of oil and brine within a relatively short time, which may lead to a given well becoming an economic failure due to the high cost of “down time” necessary for cleaning and removing the solid deposits. Sodium chloride is the most common of the products which deposit from brines. In addition to oil field applications, brines are also used as heat transfer mediums, in geothermal wells, and numerous other uses. Regardless of the use, when brines saturated at a particular temperature subsequently cool, salt precipitation occurs.
Accordingly, the inhibition of salt from aqueous streams, especially from brine solutions encountered during oil and gas production, presents a formidable challenge, and a continuing need exists for a salt inhibitor which is effective at inhibiting salt formation at relatively low concentrations in the aqueous stream.